Fastener driving tool

ABSTRACT

A high pressure stud gun or fastener driving tool includes a housing providing a cylinder, a combustion chamber, and a drive track to which studs or fasteners to be driven are supplied. A piston movable in the cylinder actuates a driver slidable in the drive track. A fluid controlled main valve is normally biased by compressed air supplied to a large area valve piston surface to close communication between the combustion chamber and the cylinder. A control assembly on a housing handle supplies a metered charge of combustible material to the chamber and initiates combustion thereof. A small area valve piston surface communicating with the combustion chamber opens the main valve when the gas resulting from combustion reaches a relatively high pressure, and this gas then enters the cylinder to actuate the fastener driver through a power stroke. The control assembly also includes valving for opening and closing the main valve and for purging the combustion chamber and the cylinder of combustion products. The pressure of the compressed air supplied to the large area valve piston surface controls the pressure of the gas admitted to the cylinder, and adjustable regulators on the compressed air source control the driving force applied.

United States Patent 1191 Obergfell Nov. 26, 1974 FASTENER DRIVING TOOL[75] inventor: Allen R. Obergfell, Park Ridge, Ill.

[73] Assignee: Fastener Corporation, Franklin Park, 111.

[22] Filed: May 11, 1973 [2]] Appl. No.: 359,235

[52] U.S. Cl 227/10, 173/134, 60/26.] [51] Int. Cl. 1325c 1/08 [58]Field of Search 227/8, 9, 10, 129, 130; 173/134, 135, 136, 137, 138;60/261; 123/46 SC [56] References Cited UNITED STATES PATENTS 2,730,082l/1956 Wampach 173/134 X 3,012,549 12/1961 Bard et al. 173/134 3.042.0087/1962 Liesse 227/9 X 3,213,607 10/1965 Neumeier 60/261 3,381,672 /1968Tobias et al. 227/ X Primary Examiner-Granville Y. Custer, Jr Attorney,Agent, or F irm-Mason, Kolehmainen, Rathburn & Wyss 57 ABSTRACT A highpressure stud gun or fastener driving too] includes a housing providinga cylinder, a combustion chamber, and a drive track to which studs orfasteners to be driven are supplied. A piston movable in the cylinderactuates a driver slidable in the drive track. A fluid controlled mainvalve is normally biased by compressed air supplied to a large areavalve piston surface to close communication between the combustionchamber and the cylinder. A control assembly on a housing handlesupplies a metered charge of combustible material to the chamber andinitiates combustion thereof. A small area valve piston surfacecommunicating with the combustion chamber opens the main valve when thegas resulting from combustion reaches a relatively high pressure, andthis gas then enters the cylinder to actuate the fastener driver througha power stroke. The control assembly also includes valving for openingand closing the main valve and for purging the combustion chamber andthe cylinder of combustion products. The pressure of the compressed airsupplied to the large area valve piston surface controls the pressure ofthe gas admitted to the cylinder, and adjustable regulators on thecompressed air source control the driving force applied.

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Z5 :1 26 224 1 30 m i FASTENER DRIVING TOOL This invention relates to afastener driving tool and, more particularly, to a high pressure toolcapable of driving fasteners into such hard and dense material as steelor concrete.

Most high power tools for driving or setting fasteners such as studs inhard or dense material use a powder or propellant charge that generatesgases directly admitted to a piston-cylinder motor. This means that therate of combustion of the gases controls the driving force available atany given time during combustion with the result that there tend to bedifferences in the energy imparted to fasteners on different operations.Further, control over the power desired in any given operation isachieved by using different powder charges with the result that only arather coarse adjustment of power can be effected. In addition, the costof the discrete powder charges required for each operation of the toolis somewhat greater than desirable.

Accordingly, one object of the present invention is to provide a new andimproved high power tool for driving fasteners.

Another object is to provide a new and improved single stroke power unitof the type using a piston-cylinder motor having a gas generatingchamber and a valve controlled by the generated gas for controlling theadmission of the generated gas to the cylinder.

A further object is to provide a new and improved single stroke powertool using a combustible fuel for driving a cylinder-piston motor.

A further object is to provide a power unit for a fastener driver usinga cylinder-piston motor wherein a biased main valve seals offcommunication between the cylinder and the compression chamber until thepressure of the combustion products exceeds the main valve bias,following which the combustion products are supplied to the cylinder tooperate the motor.

A further object is to provide a single stroke fastener driving toolusing a pneumatically biased main valve subjected to the pressure of gasgenerated in the combustion chamber to control the admission ofcombustion products from the chamber to a cylinder and wherein thepneumatic bias can be regulated to control the pressure at whichcombustion products are admitted to the cylinder.

A further object is to provide a fastener driving tool using acombustion chamber to generate piston driving gases and having a new andimproved control assembly for supplying combustible material to thechamber and controlling the sequence of operation of the tool.

In accordance with these and many other objects, an embodiment of thetool having a housing having a generally vertically extending headportion and a rearwardly extending handle portion. The head portiondefines a combustion chamber, a cylinder in which is slidably mounted apiston connected to a driver element, and a fastener receiving structurein which the fastener driver is movable. Communication between thecombustion chamber and the cylinder is normally closed by a main valvehaving an actuating differential piston with a small area exposed to thecombustion chamber and a large area supplied with compressed air. Acontrol valve assembly on or in the handle includes a multipositionvalve operable to different settings to effect a sequence of operationof the tool.

In one setting, the main valve is open and compressed air is suppliedthrough the combustion chamber and the cylinder to purge these elementsof prior combustion products. In another setting, the large area surfaceon the piston for the main valve is supplied with compressed air toclose the main valve, and a metered charge of a combustible materialsuch as propane gas is supplied into the combustion chamber. In afurther setting, the metered charge of combustible gas is supplied withcompressed air to provide a combustible mixture. Operation of anelectric switch or other control renders an ignition means such as aspark plug or a glow plug effective to effect combustion of the mixturewithin the combustion chamber.

Gases evolved from the combustion of the products in the combustionchamber increase in pressure until such time as the small area surfaceon the control piston for the main valve produces a net force exceedingthe closing bias from the compressed air. At this time the main valve isshifted to its open position, and the gases from the combustion chamberenter the cylinder to drive the piston and driver through a powerstroke. These gases are vented at the end of the power stroke, and themain valve is again closed to condition the tool for a further cycle ofoperation sequenced by the control valve assembly in the manner setforth above. The cost of the fuel used to power the tool issubstantially less than the cost of the powder cartridges previouslyused. In addition, by using the valved arrangement in combination withthe combustion chamber, the power output derived from the tool can beincreased because only high pressure gases are admitted to the cylinder.Further, by regulating the pressure of the compressed air supplied forbiasing the main valve in its closed condition, the pressure at whichcombustion products enter the cylinder can be controlled with theresultant control in the driving power afforded during each stroke.

Many other objects and advantages of the present invention will becomeapparent from considering the following detailed description inconjunction with the drawings in which:

FIG. 1 is a cross sectional view of a combustion powered fastenerdriving tool embodying the present invention;

FIG. 2 is a fragmentary sectional view taken along line 22 in FIG. 1;

FIG. 3 is a sectional view taken along line 33 in FIG. 1;

FIG. 4 is an enlarged fragmentary sectional view illustrating a controlassembly in a position for effecting purging of the tool;

FIG. 5 is an enlarged sectional view similar to FIG. 4 illustrating thecontrol assembly in another or second setting for supplying a meteredcharge of combustible material to a combustion chamber in the tool;

FIG. 6 is a view similar to FIGS. 4 and 5 illustrating the controlassembly in a third setting for supplying compressed air to the fuelcharge in the combustion chamber and illustrating the tool at a momentimmediately following the ignition of thefuel in the combustion chamber;and

FIG. 7 is an enlarged fragmentary sectional view illustrating a drivepiston and driver assembly at the end of a power stroke.

Referring now more specifically to FIG. 1 of the drawings, therein isillustrated a high pressure stud or fastener driving tool which isindicated generally as and which embodies the present invention. Thetool 20 includes a housing indicated generally as 22 including agenerally vertically extending forward head portion 22A to the upper endof which is connected a generally rearwardly extending handle portionindicated generally as 22B. The head portion 22A includes a combustionchamber 24, the lower end of which communicates with the upper end of acylinder 26 in which is slidably mounted a piston 28, to the lower endof which is connected a driver element or blade 30. The driver blade 30is adapted to pass through and be slidably movable within a drive trackor opening 32 in a fastener receiving structure or nosepiece 34, thelower end of which is adapted to be placed against a workpiece intowhich a fastener or stud 36 is to be driven. A main valve or main valveassembly 38 controls communication between the combustion chamber 24 andthe cylinder 26.

A control or control valve assembly indicated generally as 40 disposedwithin or on the handle portion 228 of the housing provides means forshifting and biasing the main valve assembly 38 using a pressurizedfluid such as compressed air supplied from a compressor or othersuitable source 42. The control assembly 40 also supplies in its varioussettings a metered charge of a combustible material such as propane gasderived from a source 44 to the combustion chamber 24, in combinationwith a quantity of compressed air from the source 42. When the tool 20is in the state illustrated in FIG. 1, the combustible mixture issupplied within the combustion chamber 24, and the main valve assembly38 is biased to its illustrated closed position by compressed air.Actuation of an ignition control means indicated generally as 46connected to and including an ignition element such as a spark plug orglow plug 48 ignites the mixture within the combustion chamber 24. Whenthe pressure of the gas generated by the combustion process overcomesthe pneumatic bias applied to the main valve assembly 38, this valve isopened. and the high pressure combustion products enter the upper openend of the cylinder 26 to drive the piston 28 and the driver element 30through a power stroke during which the fastener 36 is driven into aworkpiece. After this power stroke, the control assembly 40 can beoperated to annother setting in which the main valve assembly 38 is heldopen, and compressed air is moved through the combustion chamber 24 andthe cylinder 26 to purge the tool 20 of combustion products. After thepiston 28 and the driver 30 have been manually restored to a normalposition and a fastener 36 inserted into the drive track 32, the controlvalve assembly 40 can be operated through its sequence of settings topermit another cycle of operation of the tool 20 under the control ofthe ignition control means 46. Adjustment of a regulator shownschematically as 50 permits the power of each driving stroke to becontrolled.

Referring now more specifically to the construction of the housing 22,this housing includes a generally cylindrical block or member 52 with aninner opening defining the combustion chamber 24. The open lower endofthe opening defining the chamber 24 is threaded and threadedlyreceives an internally threaded sleeve 54 to which the upper end of thecylinder 26 is threadedly connected. The upper end of the sleeve 54includes a tapered surface 54A forming a seat for the main valveassembly 38. The lower end of the cylinder 26 is threadedly secured tothe nosepiece structure 34. This structure includes a cup-shaped member56 secured in position by a set screw 58 to stabilize the tool 20 whenit is placed against a workpiece and also to prevent flying fragmentsresulting from driving the fastener 36 into the workpiece.

The main valve assembly 38 is disposed within the combustion chamber 24and includes both a combined main and exhaust valve portion 38A and anactuating or controlling piston portion 388. The valve assembly 38 isformed by a movable annular or cylindrical body 60 with a centrallydisposed opening in which is mounted a center post 62 secured to thehousing member 52 by a nut 64. To provide the main valve and exhaustportion 38A of the valve assembly 38, the body 60 is provided at itslower end with an outwardly extending portion 60A, and a flanged sleeve66 is threadedly secured within the lower end of the opening in themember 60 with an annular resilient valve member 68 interposed betweenthe flange on the sleeve 66 and the flared portion 60A of the valve body60. The resilient member 68 seats on the valve seat 54A to provide themain valve for controlling the admission of driving gases to the openupper end of the cylinder 26.

To provide an exhaust valve assembly for the upper end of the cylinder26, the lower end of the post 62 is provided with peripherally spacedrecesses 62A, and the upper interior wall of the sleeve 66 is providedwith enlarged diameter portion or opening 66A. In the closed position ofthe main valve assembly 38 shown in H6. 1, the grooves or recesses 62Aand 66A are in communication to connect the upper interior of thecylinder 26 with the space or opening within the valve body 60. Apassageway 70 in the post 64 places this opening or cavity incommunication with the atmosphere, thereby connecting the upper interiorof the cylinder 26 to the atmosphere. When, for example, the main valveassembly 38 is moved to its open position shown in FIGS. 4 and 6, thegrooves or recesses 62A and 66A are moved out of communication. and theexhaust system extending to the atmosphere including the passageway 70is closed off from communication with either the interior of thecylinder 26 or the combustion chamber 24.

The piston portion.38B of the main valve assembly 38 provides means forcontrolling movement of the main valve assembly 38 between the closedposition shown in FIGS. 1 and 5 and the open position shown in FlGS. 4and 6. The piston portion 38B includes a piston portion 60B slidablymounted within a control cylinder 72 formed in the housing member 52concentric with the post 62. The piston portion 60B includes a largearea upper surface shown as 60C and a small annular surface 60Dcontinuously communicating with or exposed to the combustion chamber 24.The area of the piston surface 60D is greater than the oppositely facingsurface of the flanged portion 60A on the valve body 60 so that when thecombustion chamber 24 is pressurized, there is a net upwardly directedcomponent of force resulting from the piston surface 60D and exposedupwardly facing surface of the flanged portion 60A.

The net effective area on the piston surface 60D tending to move themember 60 upwardly is small compared to the area of the surface 60C. Thecontrol assembly 40 includes means for supplying compressed air from thesource 42 over a passageway 74 in the mem her 52 to the control cylinder72 to provide means for biasing the main valve assembly 38 toward andholding this assembly in its closed position. The difference in theeffective areas on the piston surfaces 60C and 60D permits theattainment of extremely high pressure gases resulting from combustion inthe chamber 24 before these gases are admitted to the cylinder 26 fordriving the piston 28 by movement of the main valve assembly 38 to itsopen position. As an example, in one tool constructed in accordance withthe present invention the ratio between the area of the surface 60C andthe effective area of the surface 60D is around 18 to 1. This means thatis compressed air at a pressure of 100 psi is introduced into thecylinder 72, the main valve assembly 38 cannot be opened to admitdriving media to the cylinder 26 until the combustion products in thechamber 24 reach a pressure of 1800 psi. By regulating the pressure ofthe compressed air supplied to the cylinder 72 using the regulatingassembly 50, the pressure of the gases admitted to the cylinder 26 andthus the driving force attained on a given stroke cannot only becontrolled but can be controlled in small value increments thatpreviously could not be attained with high pressure fastener drivingtools. It is believed that the useful range of ratios between the areaof the large piston surface 60C and the effective area of the smallerpiston surface 60D include from 5 to l to as high as to l.

The control assembly or control valve assembly 40 which sequences thevarious operations of the tool 20 is carried on the handle portion 22Bof the housing 22. The handle portion 228 includes a lower handle member80 and an upper handle member 82 which are secured together and to thehousing member 52. The lower handle member 80 includes a centrallydisposed cylindrical opening 81 in which is disposed a generallycylindrical body 84 whose inner end is threadedly connected to anopening in the housing member 52 communicating with the combustionchamber 24. A flanged or enlarged outer end portion 84A on the body 84clamps the housing member 80 to the housing member 52. At its inner endthe body 84 carries a check valve assembly indicated generally as 86.

This check valve assembly selectively supplies a combustible fuel andcompressed air to the combustion chamber 24 in various settings of thecontrol valve assembly 40. The check valve assembly 86 includes (FIG. 4)a valve cylinder 88 having different diameter portions in which isslidably mounted a valve piston 90 having an enlarged head portion 90Acarrying a check valve O-ring 92. A retaining ring or washer 94 preventsdisplacement of the piston 90 from the cylinder 88 by engaging theleft-hand end of the enlarged portion 90A. This enlarged portion 90Aincludes spaced slots or recessed areas 903 to prevent sealingengagement between the washer 94 and the left-hand surface of the headportion 90A of the piston. When the piston 90 in the position shown inFIG. 4, gas is supplied over a check valve inlet passageway 96 in thehandle member 80 and passes through an opening 98 in the body 84,through the cylinder 88, and around the head portion 90A of the piston90 to be supplied to the combustion chamber 24.

A central portion of the valve body 84 in cooperation with the handlemember 80 and the opening 81 formed therein defines a combustible gasmetering chamber. More specifically, a pair of spaced O-rings 100 and102 carried on the body 84 seal off a central portion of the opening 81to provide a gas metering chamber 104 communicating with a gasinlet-outlet passageway 106 formed in the handle member 80. Acombustible gas is either supplied to the chamber 104 through thepassageway 106 or discharged from the metering chamber 104 through thepassageway 106 in dependence on the setting of the control valveassembly 40.

The right-hand or outer end portion of the valve body 84 provides ameans for coupling the tool 20 and the control assembly 40 to the sourceof pressurized fluid or compressed air 42. More specifically, acompressed air inlet line 107 from the regulating assembly 50 isthreadedly connected in the outer end of an opening 108 in the valvebody 84 and the enlarged portion 84A thereof. The opening 108 is placedin communication with a compressed air inlet passageway 110 in thehandle member 80 through a passageway 112 in the valve body 84. Althoughthe line 107 is shown as being threadedly connected to the body 84, aquick release detachable coupling can be provided.

The handle member 82 provides means for coupling the control assembly 40to the source of combustible fuel or gas 44 and also carries a manuallyadjustable control forming a part of the control valve assembly 40. Morespecifically, the handle member 82 includes a longitudinally extendingbore or opening 114, to the right-hand end of which is threadedlyconnected one end of a line 116 extending to the fuel gas outlet of theregulator assembly 50. Thus, the right-hand portion of the opening 114is normally supplied with the fuel gas. Slidably mounted within aslightly enlarged portion of the opening or cylinder 114 is acylindrical valve body 118, to one end of which a rod or adjustingmember 120 is connected so as to extend out of the opening 114 to theupper surface of the handle member 82 through a slot 122. The valvepiston 118 carries three spaced O-rings 124, 126, and 128. As the valvebody or piston 118 is shifted to its different positions, the O-rings124, 126, and 128 cooperate with a plurality of passageways or ports,all of which are numbered or indicated as 130 to selectivelyinterconnect different combinations of passageways in the handle member80 and to supply combustible gas from the right-hand portionof theopening 114 to certain passageways in the handle member 80.

In the above description, reference to the various components of thecontrol valve assembly 40 has been made with regard to FIG. 4 of thedrawings in view of the enlarged nature of this drawing. In thisdrawing, certain of the passageways such as the passageways 96 and 110are shown in schematic form to simplify an understanding of the ensuingdescription of the operation of the control valve assembly 40. FIGS. 1-3of the drawings illustrate the mechanical realization or the mechanicalform of these passageways. ln general, the various control passagewaysare formed by providing the lower handle member 80 with a flat uppersurface 80A (FIG. 2) and by forming certain of the passageways in thisflat upper surface. The upper handle member 82 is also provided with amatching flat lower surface and a sealing gasket 13] is interposedbetween these flat surfaces of the handle members 80 and 82. A pluralityof machine screws 132 then secure the two handle members 80 and 82together with the sealing gasket 131 interposed therebetween. Thepositioning and mounting of the upper handle member 82 on the housing 22is facilitated by a dowel or pin 134 extending between the left-hand endof the opening 114 and an aligned opening 136 in the housing member 52.

Referring now more specifically to FIG. 2 of the drawings, the air inletpassageway 110 throughout its greater extent is a groove or recess inthe flat upper surface 80A of the handle member 80 and terminates at itsright-hand end in a vertical passageway communieating with the opening81 in the handle member. This vertical portion of the passageway 110receives compressed air supplied through the opening 112 in the body 84.Similarly, the check valve inlet passageway 96 throughout its greaterextent comprises a groove or recess in the flat upper surface 80A of thehandle member 80. At its left-hand end a vertical portion of thepassageway 96 places this passageway in communication with the inletpassageway 98 to the check valve assembly 86. The gas passageway 106extending to the metering chamber 104 comprises a vertical passageway orbore. The flat upper surface 80A is also provided with an elongatedslot, groove, or recess 138 which is used in conveying the fuel gas fromthe chamber 114 to the metering chamber 104 over the passageway 106.

The control assembly 40 also includes further means for controlling thesupply of compressed air to the passageway 74 and thus to the controlcylinder 72. More specifically, the flat upper surface 80A of the lowerhandle member 80 includes a recess, groove, or passageway 140, theright-hand end of which is selectively supplied with compressed airunder the control of the position of the valve body 118. The left-handend of the passageway 140 terminates in alignment with one end ofapassageway 141 (FIG. 3) in the upper handle member 82. The passageway141 extends to a port at the end of the handle member 82 aligned withthe port terminating the passageway 74 in the housing member 52.

The control assembly 46 provides means for selectively igniting orinitiating combustion of the mixture within the combustion chamber 24.The assembly 46 includes an electrical switch 142 (FIGS. 1 and 3) with adepending operator element 142A engaging an upper surface on a trigger144. The trigger 144 is pivotally mounted between a pair of dependingsupports 146 by a pivot pin 148 (FIG. 3). The depending supports 146form part of a supporting bracket to which the electrical switch 142 issecured, and the bracket in turn is secured to the housing member 52 bya plurality of machine screws 150. The switch 142 controls theconnection ofthe glow plug 48 to a source of electrical current oversuitable conductors (not shown). The glow plug 48 communicates with theinterior of the combustion chamber 24 over an extension 24A of thecombustion chamber (FIG. 1). Accordingly, when the trigger 144 ispivoted in a counterclockwise direction about the pivot pin 148 toelevate the operator 142A, the switch 142 is operated to energize theglow plug or spark plug 48, thereby causing ignition of the combustiblefuel mixture within the combustion chamber 24.

To prepare the tool 20 for operation, an estimate is made of the powernecessary to drive a fastener 36 into a workpiece. The regulatorassembly 50 is then adjusted to provide the driving force necessary forthe particular fastener driving operation under consideration. Theregulator 50 can be of any of a number of types well known in the artand basically maintains the pressure of compressed air from thecompressed air source 42 and the pressure of the combustible gas or fuelfrom the source 44 in the ratio to each other affording efficientcombustion in the chamber 24. In one tool 20 constructed in accordancewith the present invention using a propane gas source 44, the regulator50 is set to provide, for example, compressed air to the line 107 fromthe source 42 at psi and propane gas from the source 44 to the line 116at five psi. If it is assumed, as in the representative example above,that there is a ratio of approximately eighteen to one between theeffective area of the piston surfaces 60C and 60D, the pressure ofcombustion products within the chamber 24 must reach 1800 psi before themain valve assembly 38 will be opened to admit generated gas to thecylinder 26. The same ratio of pressures of compressed air to fuel ismaintained by the regulator 50 in other settings. As an example, ifgreater driving power is desired, the pressure of the air supplied to thcontrol cylinder 72 is raised to 200 psi and the pressure of the propanefuel supplied by the source 44 to the line 116 is raised to ten psi. 1nthis setting, the pressure of the combustion products in the chamber 24necessary to effect opening of the main valve assembly 38 is doubledfrom 1800 psi to 3600 psi.

At the end of each driving stroke ofthe tool 20 (FIG. 7), the piston 28is at the end of its power stroke, in which position the lower surfaceof the piston 28 rests against a resilient or elastomeric bumper 152disposed within the lower end of the cylinder 26. In this position, theinterior of the cylinder 26 is vented to the atmosphere through aplurality of ports 154 designed for venting combustion products throughthe cylinder 26 at the conclusion of the power stroke of the piston 28and the driver 30. The lower end ofthe cylinder 26 also includes aplurality of peripherally spaced openings 156 of greater area designedto assist in exhausting air from the cylinder 26 below the piston 28during its power stroke. A generally cup-shaped deflector 158 isprovided for deflecting any hot gases discharged from the cylinder 26toward the workpiece and away from the operator.

The control assembly 40 is then operated to its first position in whichthe combustion chamber 24 and the interior of the cylinder 26 are purgedof combustion products and the metering chamber 104 is supplied with acharge of combustible fuel from the source 44. More specifically, inthis first position the operator on the valve piston 118 is moved to theextreme righthand position illustrated in FIG. 4 of the drawings. Inthis position, propane fuel from the line 116 contained within theopening 114 passes through the first passageway into the passageway 138and out of this passageway through the connected passageway 130 to thespace bounded by the two O-rings 126 and 128 on the valve piston 118.The fuel then flows downwardly through the passageway 106 to beaccumulated within the metering chamber 104. This fuel gas at, forexample, a pressure of around five psi also flows through an opening 160in the body 84 to be accumulated within the right-hand end of thecylinder 88 in the check valve assembly 86. This fuel biases the valvepiston 90 to its extreme left-hand position determined by engagement ofthe enlarged portion 90A of the piston with the retaining ring 94. Thisinsures that the check valve assembly 86 is opened.

In this setting of the control valve assembly 40, compressed air ataround 100 psi flows from the line 107 through the opening 108, thepassageways 110 and 112, the connected passageways 130, the check valveinlet passageway 96, the passageway 98, the cylinder 88, and past theenlarged portion 90A on the piston 90 to be supplied to the combustionchamber 24. In this setting of the control valve assembly 40, thepassageway 74 is connected to the atmosphere over the passageway 140inasmuch as this passageway terminates in a passageway 130 disposed tothe left of the O-ring 124. Since the upper surface 60C of the pistonportion 608 is connected to the atmosphere, compressed air supplied tothe combustion chamber 24 moves the main valve assembly 38 upwardly tothe position shown in FIG. 4.

This means that the compressed air supplied through the check valveassembly 86 to the combustion chamber 24 flows through the combustionchamber and the cylinder 26 to be discharged through the openings 154which are opened because the piston 28 is in the lowermost positionshown in FIG. 7. This flow of compressed air purges the chamber 24 andthe interior of the cylinder 26 of combustion products resulting fromthe prior operation of the tool 20.

The operator then moves the control valve assembly 40 to its secondposition in which the main valve assembly 38 is moved to its closedposition, and the fuel charge from the metering chamber 104 istransferred from this chamber to the combustion chamber 24. Thisposition is shown in FIG. of the drawings. In this position the operatorelement 120 is disposed substantially midway along the length of theslot 122. To assist in positioning the control valve assembly 40, theslot 122 can comprise a continuous slot along one edge and a series ofthree notches along an opposite edge to provide means for detenting thevalve assembly 40 in its desired position against the bias supplied tothe righthand end of the valve piston 118 by the fuel gas disposed tothe right of this piston within the opening 114.

In the position shown in FIG. 5 of the drawings, the O-ring 124 closesoff communication between the atmosphere and the upper end of thecontrol cylinder 72 over the passageways 74 and 140. In this position,the O-rings 124 and 126 provide communication through the adjacentpassageways 130 for supplying pressurized fluid from the passageway 110to the passageways 74 and 140. This pressurized fluid accumulates withinthe control cylinder 72 above the piston portion 60B and moves themember 60 to its lower position so that the main valve assembly 38 isnow disposed in its closed position. In this position, the resilientvalve element 68 seats on the valve seat 54A to close off communicationbetween the interior of the cylinder 26 and the combustion chamber 24.Further, the upper interior of the cylinder 26 is vented over theexhaust system including the passageway 70, the opening in the interiorof the element 60, and the recesses or grooves 62A and 66A.

When the control assembly or control valve assembly 40 is moved to thisintermediate position, the charge of combustible material in themetering chamber 104 is also transferred to the combustion chamber 24which is now sealed off from communication with the cylinder 26. Morespecifically, when the valve piston 118 is moved to the position shownin FIG. 5, the O-ring 128 closes off communication between the recess orgroove 138 and the passage 106 extending to the metering chamber 104.The O-rings 126 and 128 place the passageway 106 in communication withthe check valve inlet passageway 96 through the illustrated pair ofpassageways 130. Thus, the combustible material now flows over thepassageways 106, 130, 96, and 98 to the cylinder 88. Since the interiorof the combustion chamber 24 is substantially at atmospheric pressure,the pressurized combustible fuel gas in the cylinder 88 displaces thevalve piston to the position shown in FIG. 5 so that fuel gas enters andis confined within thecombustion chamber 24.

With the control valve assembly 40 held in this intermediate position,the operator returns the piston 28 and the driver rod 30 to the normalposition shown in FIG. 1, as by inserting an elongated rod through thedrive track 32. The operator then disposes a fastener 36 in the lowerend of the drive track 32 and places the nosepiece structure of the tool20 adjacent the workpiece. The tool 20 is now in a condition in whichthe control valve assembly 40 can be operated to its third or finalposition preparing the tool for operation.

Thus, the operator now, by manipulation of the operator member 120,moves the control valve assembly 40 to the third position shown in FIG.6 of the drawings. In this position, the metering chamber 104 isrecharged with a combustible material, and compressed air is suppliedthrough the check valve assembly 86 to the combustion chamber 24 toprovide a combustible mixture, following which the check valve assembly86 is closed.

In the third or firing position shown in FIG. 6, the 0- rings 124 and126 on the valve piston 118 maintain the supply of compressed air to thecontrol cylinder 72 so that the main valve assembly 38 is held in itsclosed position. The O-ring 128 clears the adjacent passageway 130 sothat the combustible gas from the cylinder or opening 114 is againsupplied over the passageway 106 to till the metering chamber 104. Thisgas also passes through the opening to apply a low pressure bias to thesmall area right-hand end portion of the piston 90 in the check valveassembly 86. The O-rings 126 and 128 together with the two adjacentpassageways 130 place the compressed air inlet passage 110 incommunication with the check valve inlet passage 96. This compressed airflows through the check valve assembly 86 to pressurize the combustionchamber 24 and to provide a combustible mixture within the chamber 24.As set forth above, the chamber 24 was previously pressurized with ametered charge of propane gas at 5 psi. Thus, when in the assumedexample compressed air at 100 psi is supplied through the check valveassembly 86, the chamber 24 is pressurized to 100 psi and containsapproximately 5 parts of propane gas to 95 parts of air. When thecombustion chamber 24 is thus pressurized, the check valve assembly 86is closed by movement to the position shown in dot and dash outline inFIG. 6.

More specifically, both sides of the enlarged head portion 90A of thepiston 90 in the check valve assembly 86 are subjected to pressuresaround I00 psi. However, the right-hand end of the piston 90 whichcommunicates with the interior of the metering chamber 104 through thepassageway 160 is pressurized at around 5 psi. Thus, a net force isprovided shifting the piston 90 to the right to close off communicationbetween the combustion chamber 24 and the components of the controlvalve assembly 40. The tool 20 is now in a condition to be firedinasmuch as the main valve assembly 38 is in its closed position, andthe combustible mixture has been supplied to the combustion chamber 24.

The operator then pivots the trigger 144 in a counterclockwise directionabout the pivot pin 148 to the position shown in dot and dash outline inFIG. 6. This elevates the switch operator 142A to operate the electricswitch so that the glow plug 48 is energized. After a brief time lagsufficient for the glow plug 48 to reach ignition temperature, thegaseous mixture within the combustion chamber 24 is ignited or rapidlyoxidized, and the gaseous by-products of this oxidation build up inpressure within the combustion chamber 24. In the assumed example inwhich there is an eighteen to one ratio between the effective areas 60Cand 60D and with the compressed air at 100 psi supplied to the controlcylinder 72, the gaseous products within the chamber 24, when they reach1800 psi or slightly exceed this value, produce a force acting on thepiston surface 60D which momentarily shifts the member 60 upwardly tothe position shown in FIG. 6. Atthis time, the gaseous combustionproducts, at or in excess of 1800 psi, enter the upper end of thecylinder 26 and drive the piston 28 and driver blade 30 downwardlythrough a power stroke during which the fastener 36 is driven into theworkpiece. When, by virtue of the expansion of the gaseous products fromthe combustion chamber 24 into the cylinder 26 and by virtue of ventingthe interior of the cylinder 26 when the piston reaches its lowerposition shown in FIG. 7, the differential opening the main valveassembly 38 disappears, and the bias continuously applied to the controlcylinder 72 acts on the piston surface 60C to move the main valveassembly 38 to its closed position.

When the operator releases the trigger 144 to release the switchassembly 142, the energization of the glow plug 48 is terminated. Thecontrol valve assembly 40 can then be operated through the same sequenceof three steps described above in conjunction with the further manualoperations described above to prepare the tool for its next operation.

Since the tool 20 uses only a small quantity of a low cost fuel, such aspropane gas, and a small quantity of compressed air, the cost of eachfiring stroke of the tool 20 is substantially less than that incurredusing powder charges or cartridge type tools. Further, by operation ofthe regulating assembly 50, the pressure of the compressed air suppliedto the control cylinder 72 can be varied to control the pressure atwhich the gaseous products discharged from the combustion chamber 24 areadmitted to the interior of the cylinder 26. By regulating thispressure, the power output derived from the tool 20 can easily beregulated. Further, since the regulating assembly 50 maintains thepressures of the compressed air from the source 42 and the fuel gas fromthe source 44 in step, a proper combustible mixture is always suppliedto the chamber 24 by the control valve assembly 40 in various settingsof the regulator assembly 50. Obviously, for different combustiblematerials, the proportion of air to the fuel may vary, and thesedifferences are easily adjusted in the regulating assembly 50.

Although the present invention has been described with reference to asingle illustrative embodiment thereof, it should be understood thatnumerous other modifications and embodiments can be devised by thoseskilled in the art which will fall within the spirit and scope of theprinciples of the present invention.

What is claimed and desired to be secured by Letters Patent of theUnited States is:

1. A power actuated fastener driving tool comprising a housing having aforward head portion and a rearwardly extending handle portion,

a cylinder and a fastener receiving structure included in said headportion,

fastener driving means including driver means movable relative to thefastener receiving structure and a driver operating piston slidablewithin the cylinder,

a combustion chamber in the housing,

fluid actuated valve means for controlling communication between thecylinder and the chamber to selectively admit gases from the chamberinto the cylinder,

and manually operable control means on the handle portion of the housingfor selectively supplying a combustible mixture to the chamber andcontrolling the operation of the valve means.

2. A power actuated fastener driving tool comprising a housing having acylinder and a fastener receiving structure, fastener driving meansincluding driver means movable relative to the fastener receivingstructure and a driver operating piston slidable within the cylinder, acombustion chamber in the housing, fluid actuated valve means forcontrolling communication between the cylinder and chamber toselectively admit gases from the chamber into the cylinder, said valvemeans including a pair of oppositely facing piston surfaces with a firstone of the piston surfaces communicating with the combustion chamber,manually operable control means on the housing for selectively supplyinga combustible mixture to the chamber, and regulating means coupled tothe control means and the second one of the piston surfaces forcontrolling the pressure of the gases admitted to the cylinder. 3. Thepower actuated fastener driving tool set forth in claim 2 including asource of compressed air, a source of combustible gas, and means forcoupling the source of compressed air through the regulating means tothe second piston surface and for coupling the source of combustible gasthrough the regulating means and the control means to the combustionchamber. v 4. The power actuated fastener driving tool set forth inclaim 3 in which the regulating means controls the pressure of thecompressed air supplied to the piston surface and the pressure of thecombustible gas supplied to the combustion chamber. 5. The poweractuated fastener driving tool set forth in claim 3 in which the controlmeans includes means for selectively coupling the source of compressedair to the combustion chamber.

6. A single stroke tool for driving fasteners comprising a housingdefining a cylinder,

a piston slidably mounted within the cylinder,

a fastener receiving structure,

a fastener driver actuated by the piston and movable in the fastenerreceiving structure,

a combustion chamber communicating with the cylinder,

a main valve assembly normally in a closed position closingcommunication between the cylinder and the combustion chamber andmovable to an open position placing the combustion chamber incommunication with the cylinder, said main valve assembly including apiston portion movable independently of said piston and having a biassurface and an opposed surface in communication with the combustionchamber,

fluid biasing means coupled to the bias surface on the piston portionfor holding the main valve assembly in its closed position,

means supplying a combustible mixture to the combustion chamber,

and means for igniting the combustible mixture in the combustion chamberto provide a quantity of high pressure combustion products in thecombustion chamber, said products acting on the opposed surface of thepiston portion to move the main valve assembly to its open positionagainst the bias of the biasing means to permit the combustion productsto drive the piston.

7. A power actuated tool comprising a housing including a cylinder and agas generating chamber communicating with each other,

a power output means including a piston movable within the cylinder,

valve means movable independently of said piston and having a closedposition closing communication between the chamber and the cylinder andan open position placing the chamber and cylinder in communication,

piston means controlling movement of the valve means between its openand closed positions, one surface of the piston means communicating withthe chamber,

biasing means for biasing the piston means to a position moving thevalve means to its closed position,

and generating means for generating a short duration surge of highpressure gas in the gas generating chamber to move the piston meansagainst the bias applied by the biasing means to move the valve means toits open position to admit the high pressure gas to the cylinder todrive the piston. 8. The power actuated tool set forth in claim 7 inwhich the generating means includes means for supplying a combustiblemixture to the chamber and means for igniting the mixture. 9. The poweractuated tool set forth in claim 7 in which the piston means includes adifferential piston with a small area piston surface communicating withthe chamber and with a large area piston surface, and the biasing meansapplies a continuous fluid bias to the large area piston surface.

10. The power actuated tool set forth in claim 7 including fluid controlmeans for opening and closing the valve means independent of thegenerating means. 11. The power actuated tool set forth in claim 7including purging control means operable to open the valve means and tosupply a volume of fluid through the chamber and cylinder to purge thegas therefrom.

12. A power actuated tool comprising a housing having a cylinder and acombustion chamher,

a power output unit including a piston slidable in the cylinder,

valve means movable between an open position placing the chamber incommunication with the cylinder and a closed position in whichcommunication between the chamber and the cylinder is closed,

piston means for moving the valve means and including a first pistonsurface communicating with the combustion chamber for biasing the pistonmeans to move the valve means to its open position,

a control valve assembly movable to at least two different settings,said control valve assembly including means operable in a first one ofsaid settings for supplying a combustible material to the combustionchamber, said control valve assembly including means operable in asecond one of the settings for biasing the piston means to move thevalve means to its closed position,

and means for effecting combustion of the material in the combustionchamber with the control valve assembly in its second setting togenerate pressurized gas in the combustion chamber to overcome the biasapplied to the piston means by the control valve assembly so as to movethe valve means to its open position and supply the gas in the chamberto the cylinder.

13. The power actuated tool set forth in claim 12 in which the housingincludes a control cylinder for the piston means,

the piston means includes a second piston surface for biasing the pistonmeans to move the valve means to its closed position, said secondsurface being in the control cylinder,

and the control valve assembly includes means operative in the secondsetting of the control valve assembly for supplying pressurized fluid tothe control cylinder to act on the second piston surface.

14. The power actuated tool set forth in claim 13 including means foradjusting the pressure of the pressurized fluid supplied to the controlcylinder to control the pressure of the generated gas supplied to thecylinder when the valve means is moved to its open position.

15. The power actuated tool set forth in claim 13 in which the area ofthe second piston surface is substantially larger than the area of thefirst piston surface.

16. The power actuated tool set forth in claim 12 in 5 which themetering chamber to the combustion chamber the control valve assemblyincludes means operable in the first setting of the control valveassembly. to control the piston means to move the valve 17. The poweractuated tool set forth in claim 12 in means to its open position.

1. A power actuated fastener driving tool comprising a housing having aforward head portion and a rearwardly extending handle portion, acylinder and a fastener receiving structure included in said headportion, fastener driving means including driver means movable relativeto the fastener receiving structure and a driver operating pistonslidable within the cylinder, a combustion chamber in the housing, fluidactuated valve means for controlling communication between the cylinderand the chamber to selectively admit gases from the chamber into thecylinder, and manually operable control means on the handle portion ofthe housing for selectively supplying a combustible mixture to thechamber and controlling the operation of the valve means.
 2. A poweractuated fastener driving tool comprising a housing having a cylinderand a fastener receiving structure, fastener driving means includingdriver means movable relative to the fastener receiving structure and adriver operating piston slidable within the cylinder, a combustionchamber in the housing, fluid actuated valve means for controllingcommunication between the cylinder and chamber to selectively admitgases from the chamber into the cylinder, said valve means including apair of oppositely facing piston surfaces with a first one of the pistonsurfaces communicating with the combustion chamber, manually operablecontrol means on the housing for selectively supplying a combustiblemixture to the chamber, and regulating means coupled to the controlmeans and the second one of the piston surfaces for controlling thepressure of the gases admitted to the cylinder.
 3. The power actuatedfastener driving tool set forth in claim 2 including a source ofcompressed air, a source of combustible gas, and means for coupling thesource of compressed air through the regulating means to the secondpiston surface and for coupling the source of combustible gas throughthe regulating means and the control means to the combustion chamber. 4.The power actuated fastener driving tool set forth in claim 3 in whichthe regulating means controls the pressure of the compressed airsupplied to the piston surface and the pressure of the combustible gassupplied to the combustion chamber.
 5. The power actuated fastenerdriving tool set forth in claim 3 in which the control means includesmeans for selectively coupling the source of compressed air to thecombustion chamber.
 6. A single stroke tool for driving fastenerscomprising a housing defining a cylinder, a piston slidably mountedwithin the cylinder, a fastener receiving structure, a fastener driveractuated by the piston and movable in the fastener receiving structure,a combustion chamber communicating with the cylinder, a main valveassembly normally in a closed position closing communication between thecylinder and the combustion chamber and movable to an open positionplacing the combustion chamber in communication with the cylinder, saidmain valve assembly including a piston portion movable independently ofsaid piston and having a bias surface and an opposed surface incommunication with the combustion chamber, fluid biasing means coupledto the bias surface on the piston portion for holding the main valveassembly in its closed position, means supplying a combustible mixtureto the combustion chamber, and means for igniting the combustiblemixture in the combustion chamber to provide a quantity of high pressurecombustion products in the combustion chamber, said products acting onthe opposed surface of the piston portion to move the main valveassembly to its open poSition against the bias of the biasing means topermit the combustion products to drive the piston.
 7. A power actuatedtool comprising a housing including a cylinder and a gas generatingchamber communicating with each other, a power output means including apiston movable within the cylinder, valve means movable independently ofsaid piston and having a closed position closing communication betweenthe chamber and the cylinder and an open position placing the chamberand cylinder in communication, piston means controlling movement of thevalve means between its open and closed positions, one surface of thepiston means communicating with the chamber, biasing means for biasingthe piston means to a position moving the valve means to its closedposition, and generating means for generating a short duration surge ofhigh pressure gas in the gas generating chamber to move the piston meansagainst the bias applied by the biasing means to move the valve means toits open position to admit the high pressure gas to the cylinder todrive the piston.
 8. The power actuated tool set forth in claim 7 inwhich the generating means includes means for supplying a combustiblemixture to the chamber and means for igniting the mixture.
 9. The poweractuated tool set forth in claim 7 in which the piston means includes adifferential piston with a small area piston surface communicating withthe chamber and with a large area piston surface, and the biasing meansapplies a continuous fluid bias to the large area piston surface. 10.The power actuated tool set forth in claim 7 including fluid controlmeans for opening and closing the valve means independent of thegenerating means.
 11. The power actuated tool set forth in claim 7including purging control means operable to open the valve means and tosupply a volume of fluid through the chamber and cylinder to purge thegas therefrom.
 12. A power actuated tool comprising a housing having acylinder and a combustion chamber, a power output unit including apiston slidable in the cylinder, valve means movable between an openposition placing the chamber in communication with the cylinder and aclosed position in which communication between the chamber and thecylinder is closed, piston means for moving the valve means andincluding a first piston surface communicating with the combustionchamber for biasing the piston means to move the valve means to its openposition, a control valve assembly movable to at least two differentsettings, said control valve assembly including means operable in afirst one of said settings for supplying a combustible material to thecombustion chamber, said control valve assembly including means operablein a second one of the settings for biasing the piston means to move thevalve means to its closed position, and means for effecting combustionof the material in the combustion chamber with the control valveassembly in its second setting to generate pressurized gas in thecombustion chamber to overcome the bias applied to the piston means bythe control valve assembly so as to move the valve means to its openposition and supply the gas in the chamber to the cylinder.
 13. Thepower actuated tool set forth in claim 12 in which the housing includesa control cylinder for the piston means, the piston means includes asecond piston surface for biasing the piston means to move the valvemeans to its closed position, said second surface being in the controlcylinder, and the control valve assembly includes means operative in thesecond setting of the control valve assembly for supplying pressurizedfluid to the control cylinder to act on the second piston surface. 14.The power actuated tool set forth in claim 13 including means foradjusting the pressure of the pressurized fluid supplied to the controlcylinder to control the pressure of the generated gas supplied to thecylinder when tHe valve means is moved to its open position.
 15. Thepower actuated tool set forth in claim 13 in which the area of thesecond piston surface is substantially larger than the area of the firstpiston surface.
 16. The power actuated tool set forth in claim 12 inwhich the control valve assembly includes both a combustible gasmetering chamber for supplying a given quantity of combustible gas andmeans for coupling the metering chamber to the combustion chamber in thefirst setting of the control valve assembly.
 17. The power actuated toolset forth in claim 12 in which the control valve assembly includes meansoperable to control the piston means to move the valve means to its openposition.